The use of wireless terminals to access the Internet is growing dramatically. This is due to a large extent to the availability of high speed access technologies such as GPRS specified for 2G (GSM) and 3G (UMTS) networks, as well of course to the availability of high quality content. In the case of GPRS sessions (known as PDP contexts), although users tend to be billed based upon sent and received data volumes rather than time, these cannot be considered “always-on”. Rather, a user must initiate a session from his or her terminal, and the session will remain on until some condition is met (typically until either the user terminates the session or some predefined period of non-use has elapsed in which case the terminal or network can end the session). One reason for this approach is that terminals are allocated IP addresses for use in routing traffic to the terminals, and as IP address space is limited (according to IPv4), an access network must recover unused addresses for allocation to newly arriving terminals. Another reason is that active sessions consume resources at network nodes (and at the terminal) and it is desirable to keep the number of active sessions to a minimum at any one time.
Current and future service delivery to wireless terminals will rely upon peer entities or networks having knowledge of useable IP addresses for destination wireless terminals. Consider for example an email sent by a sending entity using the SMTP protocol. The email will be routed to a node within the recipient's home domain on the basis of the domain name part of the email address. It is then necessary for the home domain to resolve the recipient's email address into an IP address. However, in the case that the destination terminal does not have an ongoing data (e.g. GPRS) session, no IP address for the terminal will be registered within the network.
Solutions for existing services have been, in the main, tailor-made. For example, in the case of the Multimedia Messaging Service (MMS), receipt of an MMS message within a network triggers the sending of an SMS to the destination terminal so as to notify the user that he or she has a message. The SMS contains a URL link to the MMS content. By accepting the message, the user causes the terminal to establish a data session and retrieve the MMS data (this may alternatively happen without user intervention). In the case of IP Multimedia System (IMS) enabled services, a wireless terminal is required to send REGISTER messages to the IMS core at regular intervals in order to maintain the session.
A similar problem arises in the case of wired terminals, and terminals attached via an always-on wireless network (e.g. WLAN) to a fixed access point for an IP access network. For example, one might consider the case of a “regular” Ethernet connected Personal Computer (PC) which can operate in a low power mode where everything except the Ethernet card is powered down. In this mode, it is likely that no IP address will be allocated to the device by the access network and, in any case, the PC would be incapable of receiving any pushed data. Any existing solutions for waking the PC up are likely to be custom designed for specific services.